Fancast is a service by the cable provider Comcast who streams dozens of popular tv shows from Battlestar Galactica to The Office and The Unit free on their website. The service is available to viewers with a US IP only which means that everyone else will not be able to view the tv shows unless they hide their IP with a service like Hotspot Shield.
The amount of tv-shows offered at FanCast is incredible, seems to be more than 100 shows that can be selected. A quick test revealed 11 full episodes of 24, 2 Numb3rs episodes, 7 30-days episodes. The usual amount seems to be between 2-10 for most shows.
Most episodes show advertisements before playing the shows but that is fine I guess, it has to be financed somehow. Resolution is 384 x 288 and the quality of the video is good enough and far superior to those of Youtube. You do get recommendations on the right side of the video and a short description of the video that you are currently viewing.
Update: Fancast has been retired. It is no longer available and will never be available again. Users from the United States can use other - legal - services such as Hulu to watch tv shows online. Users from outside the United States, ex pats for instance, can only watch the shows online when using a virtual private network or another means of using an American IP address.